CN112877773B - Non-air flow MPCVD single crystal diamond growth method using solid carbon source - Google Patents

Abstract

The invention discloses an airless MPCVD single crystal diamond growth method utilizing a solid carbon source, and aims to solve the problems that a large amount of high-purity hydrogen needs to be consumed in the existing MPCVD single crystal diamond growth process, and the utilization rate of the carbon source is low. The single crystal diamond growth method comprises the following steps: firstly, cleaning diamond seed crystals; secondly, placing single-crystal diamond seed crystals on a sample holder at the center of a sample table, and placing a solid carbon source around the single-crystal diamond seed crystals; vacuumizing the reaction cabin, introducing high-purity hydrogen, and increasing the air pressure and the microwave power; monitoring plasma in the reaction chamber by using a spectrometer in the non-air-flow stable growth process, and adjusting the temperature of the surface of the solid carbon source by adjusting the microwave power; and fifthly, ending the growth. In the non-air flow growth process, atomic hydrogen etches a solid carbon source to generate a carbon-hydrogen group, and then the carbon-hydrogen group is transported to the surface of the diamond seed crystal through thermal diffusion particles, and the process is continuously and circularly carried out, so that the rapid growth of the single crystal diamond is realized.

Description

Non-air flow MPCVD single crystal diamond growth method using solid carbon source

technical field

The invention belongs to the field of diamond material preparation, and in particular relates to a method for preparing a non-airflow MPCVD single crystal diamond using a solid carbon source as a precursor.

Background technique

Synthetic diamond technology has developed rapidly in recent decades, among which high temperature and high pressure (HPHT) and chemical vapor deposition (CVD) are the most widely used. Microwave Plasma Chemical Vapor Deposition (MPCVD) uses microwaves as the energy source, without electrode pollution, and the generated plasma has high stability and energy density, and is the most promising method for preparing large-size, high-quality single-crystal diamond materials one. In the conventional MPCVD single crystal diamond growth process, gaseous carbon sources such as methane and carbon dioxide are usually used as growth precursors, and solid carbon sources such as graphite flakes and graphite powder are also used as precursors. It is necessary to continuously introduce and discharge a large amount of mixed gas such as hydrogen or hydrogen methane during the growth process. This method not only has a low carbon source utilization rate, but also causes a large amount of waste of high-purity hydrogen. In the CVD diamond growth mechanism, the atomic hydrogen generated by hydrogen dissociation acts like a catalyst, which inhibits the generation of sp ² phase and promotes the combination of carbon dangling bonds and carbon-containing groups on the substrate surface, which itself does not consume .

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problem that a large amount of high-purity hydrogen needs to be consumed in the existing MPCVD method single crystal diamond growth process, and the carbon source utilization rate is relatively low, and a kind of gas-free MPCVD single crystal diamond growth method utilizing solid carbon source is provided .

The present invention utilizes the non-air flow MPCVD single crystal diamond growth method of solid carbon source to realize according to the following steps:

1. Ultrasonic cleaning of the diamond seed crystal through acetone, deionized water and anhydrous ethanol in sequence to obtain the cleaned single crystal diamond seed crystal;

2. Place the cleaned single crystal diamond seed crystal on the sample holder in the center of the sample table, place the solid carbon source around (around) the single crystal diamond seed crystal, and control the total area of the upper surface of the solid carbon source (that is, with the The area of plasma contact) is 10 to 25 times the upper surface area of the single crystal diamond seed;

3. The CVD reaction chamber is evacuated to below 5×10 ^-3 Pa, then high-purity hydrogen (9N) is introduced, and the air pressure and microwave power are increased until the temperature of the single crystal diamond seed crystal reaches 900-1000 °C, When the temperature of the solid carbon source is 650-800°C, the intake valve and the exhaust valve are closed, and a closed environment is formed in the CVD reaction chamber;

4. During the stable growth process without airflow, use a spectrometer to monitor the plasma in the CVD reaction chamber, and calculate the relative intensity ratio of the C ₂ (514nm) and H _α (656nm) spectral lines in the emission spectrum obtained by the test. Microwave power is used to adjust the temperature of the surface of the solid carbon source, thereby adjusting the etching rate of atomic hydrogen to the solid carbon source, and the relative intensity ratio of the C ₂ (514nm) and H _α (656nm) spectral lines is controlled between 0.25-0.55;

5. After the time required for the growth without airflow, the growth is ended, and a single crystal diamond epitaxial growth layer with a certain thickness is obtained on the surface of the single crystal diamond seed crystal.

The invention is based on the process mechanism of MPCVD diamond growth, that is, the atomic hydrogen generated by hydrogen dissociation is in dynamic circulation and is not consumed by itself. Therefore, through the use of a solid carbon source, it is not necessary to pass and flow into the reaction chamber during the stable growth process. Extract the gas. In the process of growth without airflow, atomic hydrogen etches the solid carbon source to generate hydrocarbon groups, which are then transported to the surface of the diamond seed crystal through thermal diffusion particles. After deposition and growth, atomic hydrogen is extracted. of rapid growth.

Description of drawings

Fig. 1 is the arrangement schematic diagram of single crystal diamond seed crystal and solid carbon source in the embodiment, wherein 1. is a water cooling table, 2. is a diamond seed crystal, 3. is a graphite sheet, and 4. is a molybdenum holder;

Fig. 2 is the plasma emission spectrum test chart in the non-airflow growth process in the embodiment;

3 is an optical photograph of a single crystal diamond epitaxial growth layer sample obtained after growth in the embodiment;

FIG. 4 is a Raman spectrum test chart of the single crystal diamond epitaxial growth layer sample obtained after the growth in the embodiment.

Detailed ways

Embodiment 1: This embodiment utilizes the non-air flow MPCVD single crystal diamond growth method of solid carbon source according to the following steps:

1. Ultrasonic cleaning of the diamond seed crystal through acetone, deionized water and anhydrous ethanol in sequence to obtain the cleaned single crystal diamond seed crystal;

2. Place the cleaned single crystal diamond seed crystal on the sample holder in the center of the sample table, place the solid carbon source around (around) the single crystal diamond seed crystal, and control the total area of the upper surface of the solid carbon source (that is, with the The plasma contact area) is 10 to 25 times the upper surface area of the single crystal diamond seed crystal,

3. The CVD reaction chamber is evacuated to below 5×10 ^-3 Pa, then high-purity hydrogen (9N) is introduced, and the air pressure and microwave power are increased until the temperature of the single crystal diamond seed crystal reaches 900-1000 °C, When the temperature of the solid carbon source is 650-800°C, the intake valve and the exhaust valve are closed, and a closed environment is formed in the CVD reaction chamber;

4. During the steady growth process without airflow, use a spectrometer to monitor the plasma in the CVD reaction chamber, and calculate the relative intensity ratio of C ₂ (514nm) and H _α (656nm) spectral lines in the emission spectrum obtained by the test. Microwave power is used to adjust the temperature of the surface of the solid carbon source, thereby adjusting the etching rate of atomic hydrogen to the solid carbon source, and the relative intensity ratio of the C ₂ (514nm) and H _α (656nm) spectral lines is controlled between 0.25-0.55;

5. After the time required for the growth without airflow, the growth is ended, and a single crystal diamond epitaxial growth layer with a certain thickness is obtained on the surface of the single crystal diamond seed crystal.

In the non-air flow MPCVD single crystal diamond growth process using a solid carbon source in this embodiment, except for the hydrogen gas introduced during the initial plasma ignition and boosting to the preparation conditions, there is no need to introduce and extract hydrogen during the long-term stable growth process. , significantly reducing the consumption of high-purity hydrogen, using hydrogen dissociated atomic hydrogen to etch solid carbon source and deposit diamond cycle process, improve the utilization rate of carbon source, realize the efficient use of carbon source and the rapid growth of single crystal diamond .

Embodiment 2: The difference between this embodiment and Embodiment 1 is that the material of the sample holder described in step 2 is metal molybdenum.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the purity of the solid carbon source is greater than 99.9%.

Embodiment 4: The difference between this embodiment and one of Embodiments 1 to 3 is that the solid carbon source is graphite flakes, graphite particles or graphene powder.

Embodiment 5: The difference between this embodiment and one of Embodiments 1 to 4 is that when the solid carbon source is in the form of particles or powder, the solid carbon source is placed in the groove of the sample stage, and the solid carbon source is filled with the water cooling stage. Surface is flush.

Embodiment 6: The difference between this embodiment and one of Embodiments 1 to 5 is that the distance between the solid carbon source and the single crystal diamond seed crystal in step 2 is 1-40 mm.

Embodiment 7: The difference between this embodiment and one of Embodiments 1 to 6 is that in step 3, when the temperature of the solid carbon source is 700-750° C., the intake valve and the exhaust valve are closed.

Embodiment 8: The difference between this embodiment and one of Embodiments 1 to 7 is that in step 4, the relative intensity ratio of the C ₂ (514 nm) and H _α (656 nm) spectral lines is controlled to be between 0.35-0.45.

Embodiment 9: The difference between this embodiment and one of Embodiments 1 to 8 is that in step 4, the growth without airflow is controlled for 2 to 100 hours.

Embodiment 10: The difference between this embodiment and one of Embodiments 1 to 9 is that the thickness of the single crystal diamond epitaxial growth layer in step 5 is 0.02-2 mm.

Embodiment: This embodiment utilizes the non-air flow MPCVD single crystal diamond growth method of solid carbon source to implement according to the following steps:

1. Ultrasonic cleaning of the diamond seed crystal through acetone, deionized water and anhydrous ethanol in turn, each cleaning step is 15min, to obtain a single crystal diamond seed crystal after cleaning, and the size of the diamond seed crystal is 5mm×5mm,;

2. Place the cleaned single crystal diamond seed crystal on the molybdenum holder in the center of the sample stage, and use graphite sheet (purity 99.99%) as the solid carbon source. around the diamond seed;

3. The CVD reaction chamber was evacuated to 5×10 ^-3 Pa, and then 200sccm of high-purity hydrogen (9N) was introduced, and the air pressure and microwave power were increased until the temperature of the single crystal diamond seed crystal reached 980°C. When the temperature of the solid carbon source is 720℃, close the intake valve and the exhaust valve, and a closed environment is formed in the CVD reaction chamber;

4. Start without airflow growth. During the stable growth process without airflow, use a spectrometer to monitor the plasma in the CVD reaction chamber, and calculate the difference between C ₂ (514nm) and H _α (656nm) spectral lines in the emission spectrum obtained by the test. Relative intensity ratio, adjust the temperature of the solid carbon source surface by adjusting the microwave power, thereby adjusting the etching rate of atomic hydrogen to the solid carbon source, control the relative intensity ratio of C ₂ (514nm) and H _α (656nm) spectral line to 0.42 ;

5. Stop sampling after 20 hours of no airflow growth, and obtain a single crystal diamond epitaxial growth layer of 0.36 mm on the surface of the single crystal diamond seed crystal.

Fig. 2 is the test result of plasma emission spectrum in the process of gas-free growth of the present embodiment, wherein there are strong C ₂ spectral lines and H _α spectral lines, indicating that atomic hydrogen generated by hydrogen dissociation etches carbon-containing groups out of graphite , where the relative intensity ratio of the C ₂ line and the H _α line is 0.42.

Fig. 4 is the Raman spectrum test result of the grown sample. The sharp 1332.5cm ^-1 diamond first-order Raman peak with high intensity indicates that the prepared diamond sample has high quality.

Claims (8)

1. The method for growing the non-air-flow MPCVD single crystal diamond by utilizing the solid carbon source is characterized by being realized according to the following steps:

firstly, ultrasonically cleaning diamond seed crystals sequentially through acetone, deionized water and absolute ethyl alcohol to obtain cleaned single crystal diamond seed crystals;

secondly, placing the cleaned monocrystalline diamond seed crystal on a sample holder at the center of a sample table, placing a solid carbon source around the monocrystalline diamond seed crystal, and controlling the total area of the upper surface of the solid carbon source to be 10-25 times of the area of the upper surface of the monocrystalline diamond seed crystal;

thirdly, vacuumizing the CVD reaction chamber to 5 x 10^-3Introducing high-purity hydrogen below Pa, raising the air pressure and the microwave power until the temperature of the single crystal diamond seed crystal reaches 900-1000 ℃, closing an air inlet valve and an air exhaust valve when the temperature of the solid carbon source is 650-800 ℃, and forming a closed environment in the CVD reaction chamber;

fourthly, monitoring the plasma in the CVD reaction chamber by a spectrometer in the non-air-flow stable growth process, and calculating C in the emission spectrum obtained by testing₂And H_αThe relative intensity ratio of the spectral line is adjusted by adjusting the microwave power to adjust the temperature of the surface of the solid carbon source, thereby adjusting the etching rate of atomic hydrogen to the solid carbon source and controlling C₂And H_αThe relative intensity ratio of the spectral lines is between 0.25 and 0.55;

fifthly, after the time required by the air flow-free growth is not needed, the growth is finished, and a single crystal diamond epitaxial growth layer with a certain thickness is obtained on the surface of the single crystal diamond seed crystal;

wherein the solid carbon source is graphite flake.

2. The method for growing MPCVD single crystal diamond using solid carbon source without flow according to claim 1, wherein the material of the sample holder in the second step is molybdenum.

3. The airless MPCVD single crystal diamond growth method using a solid carbon source of claim 1, wherein the purity of the solid carbon source is greater than 99.9%.

4. The airless MPCVD single crystal diamond growth method using a solid carbon source as in claim 1, wherein the spacing between the solid carbon source and the single crystal diamond seed in step two is 1-40 mm.

5. The airless MPCVD single crystal diamond growth method using a solid carbon source of claim 1, wherein in the third step, the air inlet valve and the air outlet valve are closed when the temperature of the solid carbon source is 700-750 ℃.

6. The method for non-flow MPCVD single crystal diamond growth using a solid carbon source according to claim 1, wherein C is controlled in step four₂And H_αThe relative intensity ratio of the spectral lines is between 0.35 and 0.45.

7. The method for growing the MPCVD single-crystal diamond by using the solid carbon source according to claim 1, wherein the growth in the fourth step is controlled to be carried out for 2-100 h without air flow.

8. The airless MPCVD single crystal diamond growth method using a solid carbon source according to claim 1, wherein the thickness of the step five single crystal diamond epitaxial growth layer is 0.02-2 mm.

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